It's the best of a lot of worse options. Social media is a shouting match, and newsletters are either spam filtered or ignored. People don't want to ignore it, but email is just a bad way to follow a lot of things. RSS readers offer a nice, compact list of all the things you want to read.

I don't know what the click through rate is like on RSS feeds with a statistically useful subscriber count, but Google Reader says my feed has 11 subscribers, meaning those 3 people who came through on my last post are 27%. I don't get that kind of click through with hundreds of real people following my Twitter accounts, or thousands on G+. A million social media followers is meaningless if only 10,000 of them click your links, and any publisher with sense realizes that. Email is only slightly better: http://mailchimp.com/resources/research/email-marketing-benc...